Along an assembly line, diapers, sanitary napkins, and various types of other disposable absorbent articles may be assembled by adding components to and otherwise modifying advancing, continuous webs of material. Webs of material and component parts used to manufacture diapers may include: backsheets, topsheets, absorbent cores, front and/or back ears, fastener components, and various types of elastic webs and components such as leg elastics, barrier leg cuff elastics, and waist elastics. Webs of material and component parts used to manufacture sanitary napkins may include: backsheets, topsheets, secondary topsheets, absorbent core components, release paper wrappers, and the like. In some configurations, graphics are printed on individual components and/or continuous webs of material used to assemble the absorbent articles. The graphics may be provided by printing ink on substrate materials by various printing methods, such as flexographic printing, rotogravure printing, screen-printing, inkjet printing, and the like.
In some configurations, the printing operations are performed separate to the assembly process, such as for example, printing the substrates offline wherein the printed substrates may be stored until needed for production. For example, printing operations may be accomplished on discrete printing lines, separately from converting lines that are dedicated to manufacturing disposable absorbent articles. After printing on the printing lines, the printed substrates are delivered to the converting lines, such as in a form of continuous webs comprising printed images thereon. However, the above practice of separately printing the substrates offline from the converting lines typically requires additional cost associated with handling, winding and unwinding, storing, and shipping of the substrates. In addition, the above steps can negatively affect the quality of the printed substrate, resulting in uneven and often excessive deformations of the wound layers of the substrate inside the roll due to uneven distribution of the compression forces inside the roll. Furthermore, the separately printed substrates often require special registration control methods to ensure proper phasing of the printed images with the converting operations to affect a desired and consistent positioning of the printed image in the produced article.
In an attempt to overcome the aforementioned drawbacks to offline printing, the graphic printing may be done online during the article assembly process. However, combining printing operations with converting operations may create other challenges in performing such printing processes when attempting to maintain aesthetically pleasing final assemblies. For example, contact printing processes, such as flexographic and rotogravure printing processes, may be capable of operating effectively on certain substrates at relatively high production rates. However, such contact printing processes have relatively low degrees of flexibility with regard to the ability to change the design of a printed graphic. When utilizing such contact printing methods, changes in graphic designs would often necessitate the shutdown and restart of the entire converting operation. In contrast, some types of printing processes, such as non-contact inkjet printing processes, may provide relatively high degrees of flexibility and ease with regard to the ability to change the design of a printed graphic. In some configurations, a change in graphic design can be implemented by simply inputting commands to a programmed printhead controller to select a desired image to be printed.
However, to obtain such graphics with multiple colors and relatively intricate designs, multiple printheads need to be used. These printheads extend in the cross direction to enable printing of the entire width of the substrate and also extend in the machine direction to enable printing with multiple colors and at desired resolutions. Generally, the more complex the design and the more colors of the graphic, the greater the number of printheads that need to be used. For example, when an area to be printed on a substrate is wider than the width of a single printhead, multiple printheads are stitched together, or stated another way, placed immediately adjacent to one another in the cross direction. This results in the printheads generally covering an area which extends beyond the area that needs to be printed and only a portion of the printhead is used for printing. Further, when the design requires more than one color, printheads are placed adjacent one another in the machine direction. Printheads of various colors may need to be used to color build, or stated another way, create a different color or the appearance of a different color using at least two other colors. For example, a graphic that requires the color purple would need to be printed with a printhead including cyan ink and a printhead including magenta ink. These printheads would be placed adjacent to one another in the machine direction. Generally the greater the number of colors a graphic requires the greater the number of printheads required. The printheads are relatively costly and often require backup printheads to ensure that production is not adversely impacted by a malfunctioning printhead.
Consequently, there remains a need to minimize the number of printheads while still maintaining the ability to produce products having multi-colored graphics and the ability to communicate product benefits to the consumer.